Chelant-enhanced washing of CCA-contaminated soil: Coupled with selective dissolution or soil stabilization

Jingzi Beiyuan; Abbe Y T Lau; Daniel C W Tsang; Weihua Zhang; Chih-Ming Kao; Kitae Baek; Yong Sik Ok; Xiang-Dong Li

doi:10.1016/j.scitotenv.2017.09.015

Chelant-enhanced washing of CCA-contaminated soil: Coupled with selective dissolution or soil stabilization

Sci Total Environ. 2018 Jan 15:612:1463-1472. doi: 10.1016/j.scitotenv.2017.09.015. Epub 2017 Sep 25.

Authors

Jingzi Beiyuan¹, Abbe Y T Lau¹, Daniel C W Tsang², Weihua Zhang³, Chih-Ming Kao⁴, Kitae Baek⁵, Yong Sik Ok⁶, Xiang-Dong Li¹

Affiliations

¹ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
² Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China. Electronic address: dan.tsang@polyu.edu.hk.
³ School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China.
⁴ Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan.
⁵ Department of Environmental Engineering, Chonbuk National University, Jeollabuk-do 561-756, Republic of Korea.
⁶ O-Jeong Eco-Resilience Institute (OJERI), Division of Environmental Science and Ecological Engineering, Korea University, Seoul, Republic of Korea.

PMID: 28903175
DOI: 10.1016/j.scitotenv.2017.09.015

Abstract

Remediation of CCA-contaminated soil (Cr, Cu, and As) by biodegradable chelant-enhanced washing (EDDS, S,S-ethylene-diamine-disuccinic-acid) needs further enhancement. This study investigated the effectiveness of coupling with pre-treatment by selective dissolution and post-treatment by soil amendments, respectively. Three groups of reagents (reductants, alkaline solvents, and organic ligands) were adopted in the pre-treatment to dissolve the oxide minerals before EDDS extraction. In the post-treatment, soil amendments (coal fly ash (CFA), acid mine drainage sludge (AMDS), green waste compost (GWC)), and their mixtures) were used for a 2-month stabilization after 2-h EDDS washing. Multi-endpoint evaluation was performed by assessing the chemical state, leachability, mobility, bioaccessibility, and plant-availability of residual metal(loid)s as well as the cytotoxicity, enzyme activities, and available nutrients of the treated soils. Pre-treatment by dithionite-citrate-bicarbonate significantly enhanced extraction efficiency, but also increased the leachability of As and Cr and bioaccessibility of Cr in the treated soils. While sodium hydroxide removed the majority of As without increasing its leachability and bioaccessibility, it increased the cytotoxicity and inhibited the acid phosphatase activity. Post-treatment with AMDS and CFA effectively controlled the mobility and leachability of residual As and Cr after EDDS washing. However, destabilized Cu was only marginally immobilized by GWC due to strong Cu-EDDS complexation. The bioaccessibility and phytoavailability of Cu was primarily reduced by EDDS washing, while those of As and Cr could be attenuated by AMDS and CFA. This study indicates that coupling chemical extraction with subsequent soil amendment plays complementary roles in mitigating effects of residual metal(loid)s and improving environmental quality.

Keywords: Arsenic; Biodegradable chelant; Chromium; Fly ash; Soil amendment; Soil washing.